Vehicles often include a hydraulic braking system for reducing the speed of the vehicle and/or maintaining the vehicle in a stopped position. Hydraulic braking systems include a master cylinder fluidly coupled to one or more hydraulic cylinders. The master cylinder includes an input shaft, which activates the hydraulic cylinders in response to the input shaft moving in a braking direction. Typically, a user moves the input shaft in the braking direction by depressing a foot pedal. Each activated hydraulic cylinder moves one or more brake pads against a drum, rotor, or other rotating element to brake the vehicle. Releasing pressure upon the foot pedal, such that the foot pedal moves in a release direction to a deactivated position, causes the input shaft to move in the release direction, which deactivates the hydraulic cylinders and permits the drum, rotor, and/or other rotating elements to rotate freely.
To reduce the force applied to the foot pedal when braking the vehicle, most hydraulic braking systems include a pneumatic brake booster. Some users find that moving a master cylinder input shaft that is coupled directly to a foot pedal requires the user to impart a force upon the foot pedal in excess of that which may be comfortably and repetitively applied. To this end, the pneumatic brake booster amplifies the force exerted on the foot pedal such that the user may move the input shaft of the master cylinder with correspondingly less force being exerted on the foot pedal.
In general, the pneumatic brake booster includes a housing, a valve shaft, a shell, a diaphragm, and a valve. The diaphragm is coupled to the input shaft of the master cylinder, the housing, and the shell. The diaphragm divides an internal cavity of the shell into a booster chamber and a vacuum chamber. The valve separates the booster chamber into an atmosphere chamber and a working chamber. Vacuum generated by a gasoline engine or a vacuum pump is coupled to the vacuum chamber, such that the vacuum chamber is maintained at a pressure less than the atmospheric pressure. The valve shaft, which is coupled to the valve and the brake pedal, is configured to open the valve in response to the brake pedal moving in the braking direction. Biasing members close the valve in response to the brake pedal moving in the release direction.
When the valve is closed, vacuum is supplied to the working chamber, such that the working chamber and the vacuum chamber are maintained at the same pressure level. The approximately equal pressure on each side of the diaphragm causes the diaphragm to remain stationary.
When a user exerts a force upon the brake pedal, the booster amplifies the force, such that the user may move the input shaft of the master cylinder more easily. As described above, exerting a force on the brake pedal causes the valve to open. As a result, air from the atmosphere is drawn through the atmosphere chamber and the valve, and then into the working chamber. The imbalance of pressure between the vacuum chamber and the working chamber tends to move the diaphragm, the valve shaft, the valve, and the input shaft of the master cylinder in the braking direction. Accordingly, the imbalance of pressure amplifies the force exerted on the brake pedal, thereby making the braking system easier to operate.
As explained above, opening the valve results in airflow between the atmosphere chamber and the working chamber. However, the construction of typical brake boosters includes elements positioned within the atmosphere chamber that may impede the airflow. While such elements are often needed for proper operation of the brake booster, it would be advantageous to provide a brake booster that increases the airflow through the atmosphere chamber, thereby increasing the efficiency of the brake booster.